I. Field of the Invention
This invention relates to a gas supply coupling for delivering natural gas to the combustion chamber of a water heater and, in particular, to a coupling incorporating a shield which retards disconnection of the supply assembly without removal of the complete assembly.
II. Description of the Prior Art
Domestic water heaters use either electricity or a combustible fuel to heat a supply of water for use on demand by the homeowner. The fuel may include heating oil, propane or natural gas which are delivered to a combustion chamber proximate the water tank. The fuel is combusted within the combustion chamber to heat and maintain the water at a predetermined temperature. In order to service and deliver fuel the combustion element, the combustion chamber is typically open to the exterior of the water heater. This can create a path for other gases to reach the combustion element.
Prior art water heater combustion chambers eliminate exterior combustion by utilizing a functionally sealed combustion chamber which controls the gas flow exteriorly of the chamber. The sealed chamber introduces manufacturing and assembly problems. A sealed chamber eliminates many of the assembly tolerances between the control unit/regulator and burner. In addition, the gas supply must pass through a sealed door for delivery of the combustion fuel. The prior known sealed doors include a burner supply tube upset on both sides of the barrier. This provided the rigid attachment required for the burner but the resultant assembly was difficult to make with the regulator or control units.
The present invention overcomes the disadvantages of the prior known gas supply couplings for water heaters by providing an integral supply coupling and combustion element with a shield to close the opening to the combustion chamber.
The supply coupling of the present invention generally includes a supply tube having an outlet through which the fuel is delivered for combustion proximate the water tank, a shield configured to close off the opening to the combustion chamber, a connector extending through the shield, and a gas supply line attached to the connector. The connector extending through the shield is designed such that the gas supply coupling can only be disassembled with specialized tools. To accomplish this, the entire supply coupling must be removed from the combustion chamber ensuring that the fuel will not be burned without the shield in place.
The connector extending through the shield includes a bulkhead fitting connected to the supply tube and having a male end extending through a similarly configured aperture in the bulkhead shield. In one embodiment, the bulkhead fitting includes staking which engages the shield to prevent rotation of the fitting in the bulkhead aperture. As an alternative, a lock nut may be mounted to the exterior end of the fitting until the shield is captured between the lock nut and the head of the fitting. The gas supply line is threadably attached to the male end of the fitting which is extending through the shield. In a preferred embodiment, the threaded fastener of the gas supply line has a tamper-proof exterior configuration requiring a specially configured tool to disengage the fastener of the supply line.
The bulkhead fitting of the present invention is physically staked to the door or bulkhead. The portion of the fitting passing through the bulkhead has a non-circular cross-section to facilitate alignment and resist rotation. The tolerances between the opening in the bulkhead and fitting passing therethrough are minimal in order to prevent a flame from passing through. To dissuade disassembly of the bulkhead the fitting connector was designed with a non-standard profile nut which will not mate with traditional tools.
Alternate embodiments of the connector include a bulkhead fitting welded to the bulkhead instead of staked or the use of a jamb nut on the outside of the bulkhead. The purpose of the tamper resistant nut is to direct service personnel to the proper connector at the control device to disassemble the supply line.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.